/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.db.rescon;

import org.apache.iotdb.db.conf.IoTDBConfig;
import org.apache.iotdb.db.conf.IoTDBDescriptor;
import org.apache.iotdb.db.engine.memtable.IMemTable;
import org.apache.iotdb.db.engine.memtable.PrimitiveMemTable;
import org.apache.iotdb.db.exception.WriteProcessException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class MemTableManager {

    private static final IoTDBConfig CONFIG = IoTDBDescriptor.getInstance().getConfig();

    private static final Logger logger = LoggerFactory.getLogger(MemTableManager.class);

    private static final int WAIT_TIME = 100;
    public static final int MEMTABLE_NUM_FOR_EACH_PARTITION = 4;
    private int currentMemtableNumber = 0;

    private MemTableManager() {
    }

    public static MemTableManager getInstance() {
        return InstanceHolder.INSTANCE;
    }

    public synchronized IMemTable getAvailableMemTable(String storageGroup)
            throws WriteProcessException {
        if (CONFIG.isEnableMemControl()) {
            currentMemtableNumber++;
            return new PrimitiveMemTable(CONFIG.isEnableMemControl());
        }

        if (!reachMaxMemtableNumber()) {
            currentMemtableNumber++;
            return new PrimitiveMemTable();
        }

        // wait until the total number of memtable is less than the system capacity
        int waitCount = 1;
        while (true) {
            if (!reachMaxMemtableNumber()) {
                currentMemtableNumber++;
                return new PrimitiveMemTable();
            }
            try {
                wait(WAIT_TIME);
            } catch (InterruptedException e) {
                logger.error("{} fails to wait for memtables {}, continue to wait", storageGroup, e);
                Thread.currentThread().interrupt();
                throw new WriteProcessException(e);
            }
            if (waitCount++ % 10 == 0) {
                logger.info("{} has waited for a memtable for {}ms", storageGroup, waitCount * WAIT_TIME);
            }
        }
    }

    public int getCurrentMemtableNumber() {
        return currentMemtableNumber;
    }

    public synchronized void decreaseMemtableNumber() {
        currentMemtableNumber--;
        notifyAll();
    }

    /**
     * Called when memory control is disabled
     */
    private boolean reachMaxMemtableNumber() {
        return currentMemtableNumber >= CONFIG.getMaxMemtableNumber();
    }

    /**
     * Called when memory control is disabled
     */
    public synchronized void addOrDeleteStorageGroup(int diff) {
        int maxMemTableNum = CONFIG.getMaxMemtableNumber();
        maxMemTableNum +=
                MEMTABLE_NUM_FOR_EACH_PARTITION * CONFIG.getConcurrentWritingTimePartition() * diff;
        CONFIG.setMaxMemtableNumber(maxMemTableNum);
        notifyAll();
    }

    public synchronized void close() {
        currentMemtableNumber = 0;
    }

    private static class InstanceHolder {

        private static final MemTableManager INSTANCE = new MemTableManager();

        private InstanceHolder() {
        }
    }
}
